Abstract: The effect of different salinities (5, 10, 15, 20, 25, 30 (control), 35, 40, and 45) on survival and growth of Zostera marina seedlings were examined under laboratory conditions, to determine their salinity suitability during a period of 30 days. The results showed that the seedlings exposed to salinities of 5 and 10 began to rot rapidly and all died during the first 10 days. Survival rate of seedlings under salinities of 20-45 ranged from 49% to 58%, which were significantly higher than those of seedlings under low salinities (5-15) (P<0.05). Seedling morphometrics and growth rate were greatest under salinity 20, in which sheath length, root length and root elongation rate of seedlings were significantly higher than those of seedlings attained in control and other salinity treatments (P<0.05). Total leaf area per shoot and leaf elongation rate under salinity 20 were not significantly different from those attained under control treatment (P>0.05) but significantly higher than those attained in salinities of 15, 35, 40 and 45 (P<0.05). Suitability analysis suggests that Z. marina  seedlings can survive in a salinity range from 15 to 45; however, the suitable salinity range for their growth is from 20 to 30.

Key words: Medlyn model, Jarvis model, Li-6400 portable photosynthesis system, Ball-Berry model, Leuning model, leaf net photosynthetic rate